One of the problems in hydraulic pumps often relates to premature wear caused by cavitation. Cavitation occurs when a liquid is subject to rapid changes of pressure, causing formation of ‘cavities’ or ‘air bubbles’ within the liquid. The bubbles can then implode, causing an erosion of metal parts of the pump. Cavitation is often accompanied by vibration and noise, which are unwanted side effects.
A pump is a system for sucking and discharging a fluid. The main characteristics of a pump are its debit and its pressure (during suction and discharge). Cavitation occurs in a pump when during suction, the available debit is lower than the debit required by the pump. For example, for a pump requiring a debit of three Gallons Per Minute (GPM) at suction, if only two GPM are available, then cavitation occurs. Conversely, if three or more GPM are available at suction, there is no cavitation. To avoid cavitation, the absolute pressure at suction shall be greater than the required Net Positive Suction Head (NPSH). NPSH value is usually supplied by manufacturers of hydraulic pumps.
However, it is not always possible to ensure that the available debit will not suddenly drop of fluctuate during functioning of the pump. There is therefore a need for a mechanism for reducing impacts of available fluid pressure variation of a hydraulic pump.